Polythioetherdithiols and process for producing same



2 m n. Eiw zszwzo m v n m m b A. A. OSWALD ET AL Filed NOV. 30, 1964 E E 12m N N N m zu ro xoRzs :8

Alexis A. Oswald Kur| Griesbclum Inventors Donlel N. Hull 7 B, c. EjMA Patent Attorngyr Sept. 24, 1968 POLYTHIOETHERDITHIOLS AND PROCESS FOR PRODUCING SAME 2QEuxw o 33 *0 Eg mnm mucucowmm 0:232 628 United States Patent ABSTRACT OF THE DISCLOSURE Allene is reacted with aliphatic, and aromatic dithiols in a selective free radical process primarily via diterminal attack to form novel thiol and/ or allyl terminated difunctional polythioetherdithiols useful as elastomer, mastics and adhesives intermediates and as constituents for room temperature curable rubbers, sealants, etc. Inherent to their unique synthesis these polymer intermediates contain the structural units derived from the dithiol and the allene in an alternating fashion and exhibit some dispersed branching resulting from center attack side reactions.

This invention relates to the prepartion of polythioetherdithiols and more specifically relates to the preparation of such dithiols by the addition of dithiols to allene.

where This reaction gives a polymeric backbone which is the result of stepwise additions. The use of a large excess of allene result in the formation of diallylic adducts:

As a by-product, polymeric residues with al,lylic end groups are obtained:

Thus the product of this invention can be represented by the following general formula:

Where T and U are each hydrogen or allyl, R is a divalent hydrocarbylene radical such as alkylene, arylene, or

aralkylene, and x and y are the same as above.

The formation of trimethylene-bis-sulfide polymer units subscribed by x is apparent by the result of further thiol additions to the allylic primary adducts of allene. The intermediates for the propylene-bis-sulfide polymer units It has been known (Organic Reactions, Edited by Subscribed y 3 are P y the P P Y derivatives of C. Cope, Vol. 13, Chapter 4: Formation of Carbon- Hetero Atom Bonds by Free Radical Chain Additions to Carbon-Carbon Multiple Bonds by F. W. Stacey and J. F. Harris, Jr., page 184, J. Wiley & Sons, Inc., NeW York,

New York, 1963) that radical additions of dithiols to di- 4 olefins may lead to polymeric materials. Unconjugated diolefins were found satisfactory starting materials. However, conjugated diolefins which are more readily available petrochemical starting materials were unsatisfactory the following postulated reaction:

2CH =C=OH +HSRSH oH =o-sRsC=CH2 (EH3 CH3 0 These intermediates, if formed, apparently react very fast LL JXL Jyl.

This is due to the fact that both the propenyl and allyl compounds react with thiols at faster rates than allene itself.

Increasing the excess of the dithiol results in decreasing the molecular weight. In case of large excess the product is the following diadduct:

HSRSCH CH CH S-R SH with some of the isomeric compound:

HS-RSCH-rOH-S-RSH The allylic oligomers, of course, may be reacted with more of the same or different dithiol. In turn, the polythioether dithiol may be reacted with more allene.

3 All these various additions to the olefinic double bonds take place 'by a free radical mechanism. This requires the initial formation of a thiyl radical.

This radical, in turn, reacts with the olefin toform an intermediate radical which on reacting with the thiol regenerates the thiyl radical in a chain fashion:

Suitable dithiols include polymethylene dimercaptans such as dior trimethylene dimercaptan, 1,2-propanedithiol, or their amino, chloro, bromo, cyano or aromatic substitution products such as xylene dithiol; various isomeric benzeneand naphthalenedithiols or their alkyl substituted products; toluenedithiols, xylenedithiols, etc.

The preferred dithiol reactants are the C to C polymethylene dimercaptans such as ethane dithiol, trimethylene dithiol, and 1,2-propane-dithiol. Aromatic dimercaptans such as xylylene dithiol are also useful.

The above-described reaction is normally carried out in the presence of a catalyst. The catalysts employable in the novel reaction of this invention are free-radical type initiators and include ultraviolet light, gamma radiation and a wide variety of peroxidic and azo compounds, Typical free-radical initiators are cumene hydroperoxide, tertiary butyl hydroperoxide, bis-tertiary butyl peroxide, and bis-azo-isobutyronitrile. When free-radical initiator compounds are employed, they will normally constitute 0.01 to weight percent, preferably 0.1 to 5 weight percent, based on allene, of the reaction mixture. In a preferred embodiment, the free-radical catalyst is a combination of a peroxidic or azo compound and ultraviolet initiation. It has been found that ultraviolet irradiation accelerates the free-radical initiator compound decomposition, thereby resulting in an effective chain initiation and, consequently, high yields of the desired products in a short reaction period.

A wide variety of reaction conditions may be employed in the process of the present invention. Suitable reaction temperatures are in the range of 100 to +120 C., preferably -70 to +100 C., for example C. The reaction pressure is not critical and superatmospheric, as well as atmospheric, pressures may be employed in the reaction period. Typical reaction pressures are in the range of 0 to 750 p.s.i.g. and preferably 10 to 150 p.s.i.g., for example, 50 p.s.i.g. In a preferred embodiment, the reaction is carried out at room temperature in a sealed reaction chamber. Such a procedure has the effect of creating a pressure in the range of 40 to 120 p.s.i.g. due to the vapor pressure of the allene gas.

The ratio of allene to dit-hiol will vary depending upon the number of thiol groups desired in the final product and may vary between 0.05 and 3 moles of dithiol per mole of allene.

The polyaddition process goes through neutral, stable intermediates which have decreasing reactivity with increasing molecular weight. Above 3000 molecular weight this usually becomes a limiting factor. In any case the polymer is thiol and/ or allyl terminated and thus is chemically reactive. The products of the invention are thus suitable as intermediates in the preparation of various higher molecular weight products.

Reactions of the polymer of this invention with trifunctional or polyfunctional molecules lead to three-dimensional polymer networks. For example, the polymer of this invention may be reacted with polybutadiene or the copolymer of butadiene and styrene such as the polymers described in US. Patent Nos. 2,712,562, 2,791,- 6 18, 2,849,510 and 2,826,618, and the like. Thus, the polythioether dithiols of this invention are especially promising intermediates for the preparation of elasto- 7 4 mers such as rubbers, foams, and the like and are particularly suited as constituents for room temperature curable rubbers, sealants, etc.

The invention will be further understood by reference to the following illustrative examples.

Example 1.Addition of ethanedithiol to allene A stirred mixture of 23.5 grams 0.25 mole) of 1,2- ethanedithiol, 12 grams (0.3 mole) of allene and 0.09 gram (0.001 mole) of t-butyl hydroperoxide catalyst in a sealed quartz tube was irradiated by a 100 watt Hanau medium pressure ultraviolet immersion lamp for ninety minutes at 15 C. By the end of this period half of the contents of the tube were converted to the solid dithiol polymer and consequently it became impossible to continue the stirring of the reaction mixture. Therefore, the mixture was melted by heating it to 42 C. and the addition was completed at the temperature in fifteen more hours.

The product was a semisolid polythioether which could be purified by dissolution in benzene and reprecipitation by an excess of methanol to yield a solid product. A nuclear magnetic resonance (N.M.R.) spectrum of the polymer (shown in FIGURE 1) indicated that it contained dimethylene, trimethylene, and propylene units bonded through sulfur. N.M.R. indicated and a potentiometric titration by silver nitrate proved that the polymer had thiol end groups. Assuming a dithiol polymer, the molecular weight was 1500 on the basis of the potentiometric titration.

Analysis.-Calcd. for

HSCH CH (SCH CH CH SCH CH SH C H S (Molecular Weight, 1457): C, 42.87; H, 8.71; S, 48.42. Found: C, 44.28; H, 7.88; S, 47.44. Osmometn'c molecular weight, 1404.

Example 2.Addition of trimethylenedithiol to allene at ambient temperatures Allene was bubbled into 54 grams (0.5 mole) of trimethylene dithiol in a quartz tube at 15 with ultraviolet light irradiation for eleven hours. During this period 16 grams (0.4 mole) of allene was absorbed and the reaction mixture solidified to yield the raw polytrimethylenesulfide dithiol. By a repeated benzene dissolution-methanol reprecipitation procedure 50 grams (84.5%) of a purified polymer having an average molecular weight of 850 was obtained. N.M.R. again indicated and potentiometric titration by silver nitrate proved that the polymer had thiol end groups. Assuming a dithiol polymer, the potentiometric titration indicated a molecular weight of 837.

Analysis.-Calcd. for C27H56S1Q (for H (SCH CH CH 8H with a molecular weight of 701.5): C, 46.24; H, 8.04; S, 45.72. Found: C, 45.33; H, 7.06; S, 45.05.

Example 3.Addition of trimethylenedithiol to allene at C.

A mixture of 19.5 grams (0.5 mole) of allene and 19.9 grams (0.18 mole) of 1,3-propanedit hi0l was irradiated by ultraviolet light for six hours while being kept in an isopropanol Dry Ice bath at about 75 C. The resulting mixture was then fractionated by distillation in vacuo. As a forerun 4 grams (21%) of propanedithiol was recovered. Then 13 grams of 3-allylrnercaptopropanethiol and other liquid oligomeric adducts were obtained between 27-92 C. at 0.5 mm. The residue (12 grams) was a very viscous oily polymeric polythioether.

Analysis.Found: C, 44.85; H, 7.37; S, 47.95.

Example 4.Addition of trimethylenedithiol to an excess of allene A magnetically stirred mixture of 16.2 grams (0.15 mole) of trimethylenedithiol and 72 grams (1.8 mole) of 6 allene was U.V. irradiated at 16 C. for twenty-four hours The advantages of the present invention having been in a closed quartz pressure tube. The reaction mixture thus fully set forth and specific examples of the same then was reacted to recover most of the unreacted allene. given, what is claimed as new and useful and desired to The residue was analyzed by N.M.R. spectroscopy. Acbe secured by Letters Patent is: cording to the spectrum it contained trimethylene 5 1. A polymeric composition of matter [S(CH S] vs. propylene [SCH CH(CH )S] units in a 5 to 1 ratio- SRS-CH CH CH SRS CH OH-BLSRSU Fractional distillation of the residue in vacuo yielded l\ 2 l l I 13 grams (46%) of diallyl trimethylene-bis-sulfide, boilx bHa y :1

ing between 82-88 at 0.3 mm. pressure.

The residue 115 grams is a liquid polymer with a where T and U are each chosen from the group connumber average osmotic molecular weight of 449. Its sisting hyclmgen and allyl R is divalenl l N.M.R. spectrum indicates that it has allylic end groups. carbylene mdlcal chosen from group conslstmg of xylylyl, naphthyl, tolyl, and xylyl, and x and y are num- The trimethylene vs. propylene ratio is 5 to 1. Calcd. for hers from 0 to 100 and n is a number betwean 2 and 26.

2. As a composition of matter a polymeric compound Of the structure (mol. wt. 485): C, 52.02; H, 8.31; S, 39.67. Found: C, 54.14; H, 8.23; S, 38.30.

Example 5.Addition of an excess of trimethylene where x, y and n are numbers from 1 to and T and U are chosen from the group consisting of hydrogen and dithiol to allene 25 anyl A mixture Of 76.4 grams (0.7 mole) of trimethylene 3, As a composition of matter a polymeric compound dithiol and 14 grams (0.35 mole) of allene were reacted of the structure T%:s om)rozocmcmcononm] [swnmolccmomconormsomcnj S(CHz)k(CO )COzCHgCCHgOflCHzh-S-U x Cfig y n at 16 C. for six hours under the elfect of ultraviolet irwhere k equals 1 to 2, x, y and n) are numbers from 1 radiation in the manner described in the earlier examples. to 25 and T and U are each chosen from the group The resulting product was heated to 215 C. at 0.05 mm. hydrogen and allyl. pressure to remove the unreacted trimethylenedithiol as 4. As a composition of matter a polymeric compound a distillate. The nuclear magnetic resonance spectrum of of the stnucture T i S SCH2CHzCH2 l S SCHz(l3H ll S S-U lL C J. LC ll. the resulting liquid residual product indicated that is was where x, y and n are numbers from 1 to 25 and T and U essentially the diadduct are chosen from the group hydrogen and allyl.

HSCHZCHZCHZSCHZCHzCHZSCHZCHZCHZSH 5. As a composition of matter a compound of the structure Examples 69.--Polyaddition of different dithiols to allene HSRSCHzCHSRSH In the following experiments different dithiols (0.1 m.) H3

Were placed in a quartz pressure tube equipped with a magnetic stirrer and a Teflon-clad screw seal. The tube contents were frozen at 70 and the tube was evacuated where R is a divalent C to C alkylene radical. 5O 6. As a composition of matter a compound of the at an oil pump. Then 5.8 ml. (at 70, 1 atoms.) of alstructure lene (0.1 m.) was distilled into the tube which was then 2= 2 2 2 2 2 Z sealed. The reaction mixture was irradiated at 1720 7. A a composition of matter, a compound of h with a UV. lamp from a distance of 5 cm. The tube was tru ture then opened and the unreacted allene allowed to evap- HSCH2CH2CH2SCHZCHZCHZSCHzCHzCHZSH orate. The crude products were stirpped at 100-150/ 1-5 mm. by drawing nitrogen through them and then dissolved As a composltlon of matter a compound of the in an approximately equal volume of benzene and pre- Structure cipitated as oily liquids by dropping into 5 volumes of a z( z z z a z)m methanol. After drying to constant weight in vacuo, the 9. As a composition of matter, a compound of the viscous liquid products were analyzed. A summary of the structure experiments and their results are shown in Table I. H(SCH CH CH SH TABLE I.-ADDITION OF VARIOUS DITHIOLS TO ALLENE Initiator (1 mole Irradiation, Crude yield, Osmometrie Elemental Analyses, percent Exp. No. Dithiol Reagent percent) hours percent mol. wt 0 H S s HSCHT-Q-CHZSH (CHa)aCOOH 9 87 547 60.39 6.57 32. 72

7 (HSCHaCO2CH2)2 (CHa)aCOOH 48 88 1, 245 38. 13 5. 42 28. 08 HS-CH CH(OH@)SH None 48 93 1,126 46.80 8. 40 44.

9 SH None 50 757 61. 66 9. 83 21. 36

thiols and their chloro, bromo and cyano substitution 5 products; benzenedithiols, naphthalenedithiols, and xylene dithiols, at a temperature in the range of 100 to +120 C. and a pressure in the range of O to 750 p.s.i.g. in the presence of a free radical catalyst.

11. The process of claim 10 in which the dithiol is trimethylene dithiol and the catalyst is ultraviolet light.

12. The process of claim 10 in which the dithiol is 1,2-propanedithiol and the catalyst is ultraviolet light.

13. The process of claim 10 in which the dithiol is xylylenedithiol and the catalyst is a ultraviolet light.

14. The process of claim 10 in which the dithiol is biscarboxyethylene-methanethiol and the catalyst is ultraviolet light.

15. The process of claim 10 in which the catalyst is a combination of tertiary butyl hydroperoxide and ultraviolet light.

8 16. The process of claim 15 in which the dithiol is ethane dithiol and the catalyst is ultraviolet light.

References Cited UNITED STATES PATENTS 2,454,099 11/ 1948 Signaigo 260609 2,563,383 8/1951 Vaughan et a1. 260609 3,070,580 12/1962 Harmon 26079 OTHER REFERENCES Griesbaum et al.: J. Org. Chem, vol. 28, pp. 1952- 1957 (1963).

Van der Ploeg et al.: Rec. Trav. Chem, vol. 81, pp. 775-785 (1962).

Jacobs et al.: J. Org. Chem, vol. 28, pp. 26922697 (1963).

CHARLES B. PARKER, Primary Examiner.

20 D. R. PHILLIPS, Assistant Examiner. 

